1. Field of the Invention
The present invention relates generally to local oxidation of silicon (LOCOS) methods for forming isolation regions within semiconductor integrated circuit microelectronic fabrications. More particularly, the present invention relates the local oxidation of silicon (LOCOS) methods for forming, with enhanced properties, isolation regions within semiconductor integrated circuit microelectronic fabrications.
2. Description of the Related Art
Semiconductor integrated circuit microelectronic fabrications are formed from semiconductor substrates within and upon which are formed semiconductor devices, such as but not limited to resistors, transistors, diodes and capacitors. In turn, the semiconductor devices formed within and upon the semiconductor substrates are connected and interconnected with patterned microelectronic conductor layers which are separated by microelectronic dielectric layers.
Common in the art of semiconductor integrated circuit microelectronic fabrication is the use of isolation methods for forming isolation regions which are employed for isolating active regions of a semiconductor substrate within and upon which are formed semiconductor devices. Such isolation methods for forming isolation regions which are employed for isolating active regions of a semiconductor substrate within and upon which are formed semiconductor devices are typically intended to provide electrical isolation to the semiconductor devices such as to provide enhanced semiconductor integrated circuit microelectronic fabrication performance and reduced semiconductor device cross-talk.
Of the isolation methods and isolation regions which may be employed for isolating active regions of a semiconductor substrate, local oxidation of silicon (LOCOS) isolation methods and local oxidation of silicon (LOCOS) isolation regions are particularly common in the art of semiconductor integrated circuit microelectronic fabrication. As is understood by a person skilled in the art, local oxidation of silicon (LOCOS) methods typically employ, at least in part, a silicon nitride oxidation mask which masks an active region of a silicon semiconductor substrate, while an adjacent exposed region of the silicon semiconductor substrate is thermally oxidized within a thermal annealing oxidizing environment to form therefrom a local oxidation of silicon (LOCOS) isolation region which bounds the active region of the silicon semiconductor substrate.
While local oxidation of silicon (LOCOS) methods have become quite common in the art of semiconductor integrated circuit microelectronic fabrication for forming local oxidation of silicon (LOCOS) isolation regions within semiconductor integrated circuit microelectronic fabrications, local oxidation of silicon (LOCOS) methods and local oxidation of silicon (LOCOS) isolation regions are nonetheless not entirely without problems in the art of semiconductor integrated circuit microelectronic fabrication. In that regard, local oxidation of silicon (LOCOS) methods and local oxidation of silicon (LOCOS) isolation regions typically suffer from problems including but not limited to: (1) bird's beak encroachments of local oxidation of silicon (LOCOS) isolation regions beneath silicon nitride oxidation masks employed within local oxidation of silicon (LOCOS) methods; and (2) related silicon nitride oxidation mask physical stresses which in-part may result from bird's beak encroachments of local oxidation of silicon (LOCOS) isolation regions formed beneath silicon nitride oxidation masks employed within local oxidation of silicon (LOCOS) methods.
It is thus desirable in the art of semiconductor integrated circuit microelectronic fabrication to provide local oxidation of silicon (LOCOS) methods through which local oxidation of silicon (LOCOS) isolation regions may be formed with enhanced properties, in particular as directed towards attenuated bird's beak encroachments of local oxidation of silicon (LOCOS) isolation regions beneath silicon nitride oxidation masks employed within local oxidation of silicon (LOCOS) isolation methods.
It is towards the foregoing object that the present invention is directed.
Various local oxidation of silicon (LOCOS) methods have been disclosed in the art of semiconductor integrated circuit microelectronic fabrication for forming local oxidation of silicon (LOCOS) isolation regions with desirable properties in the art of semiconductor integrated circuit microelectronic fabrication.
For example, Wolf, in Silicon Processing for the VLSI Era, Vol. 2—Process Integration, Lattice Press (Sunset beach, Calif.) (1990), pp. 33-35, discloses a local oxidation of silicon (LOCOS) method for forming, with an attenuated bird's beak encroachment beneath a silicon nitride oxidation mask, a local oxidation of silicon (LOCOS) isolation region within a silicon semiconductor substrate within a semiconductor integrated circuit microelectronic fabrication. To realize the foregoing result, the local oxidation of silicon (LOCOS) method employs a sealed interface local oxidation (SILO) local oxidation of silicon (LOCOS) method which employs the silicon nitride oxidation mask formed directly upon the silicon semiconductor substrate, rather than formed upon a silicon oxide pad oxide layer in-turn formed directly upon the silicon semiconductor substrate.
In addition, Kobayashi et al., in U.S. Pat. No. 5,616,401, similarly also discloses a local oxidation of silicon (LOCOS) method for forming, with an attenuated bird's beak encroachment beneath a silicon nitride oxidation mask, a local oxidation of silicon (LOCOS) isolation region with a silicon semiconductor substrate employed within a semiconductor integrated circuit microelectronic fabrication. To realize the foregoing result, the local oxidation of silicon (LOCOS) method employs as an adjunct to, or in the alternative of, a silicon oxide pad oxide layer formed beneath the silicon nitride oxidation mask, a silicon oxynitride layer formed with a graded concentration of oxygen with respect to nitrogen, wherein an oxygen rich portion of the silicon oxynitride layer is formed more closely adjacent the silicon semiconductor substrate.
Further, Shim et al., in U.S. Pat. No. 5,846,596, similarly also discloses a local oxidation of silicon (LOCOS) method for forming, with an attenuated bird's beak encroachment beneath a silicon nitride oxidation mask, a local oxidation of silicon (LOCOS) isolation region within a silicon semiconductor substrate within a semiconductor integrated circuit microelectronic fabrication. To realize the foregoing result, the local oxidation of silicon (LOCOS) method employs an oxidation resistant spacer formed adjoining a sidewall of the silicon nitride oxidation mask and covering an edge portion of a pad oxidation layer formed upon a surface of the semiconductor substrate within which is to be formed the local oxidation of silicon (LOCOS) isolation region while employing the local oxidation of silicon (LOCOS) method.
Yet further, Thakur et al., in U.S. Pat. No. 6,051,511, discloses a method for forming, with attenuated physical stress, a silicon nitride oxidation mask which may be employed within a local oxidation of silicon (LOCOS) method for forming a local oxidation of silicon (LOCOS) isolation region within a silicon semiconductor substrate employed within a semiconductor integrated circuit microelectronic fabrication. To realize the foregoing result, the method employs forming the silicon nitride oxidation mask while employing a silicon nitride material which has a graded concentration of silicon with respect to nitrogen.
Still yet further, Peidous et al., in U.S. Pat. No. 6,071,793, discloses yet another local oxidation of silicon (LOCOS) method for forming, with an attenuated bird's beak encroachment beneath a silicon nitride oxidation mask, a local oxidation of silicon (LOCOS) isolation region within a silicon semiconductor substrate within a semiconductor integrated circuit microelectronic fabrication. To realize the foregoing result, the local oxidation of silicon (LOCOS) method employs the silicon nitride oxidation mask which has formed therein at a base of its sidewall a tapered foot which protrudes over and resiliently constrains the local oxidation of silicon (LOCOS) isolation region which is formed employing the local oxidation of silicon (LOCOS) method.
Finally, Brady et al., in U.S. Pat. No. 6,090,686, similarly also discloses a method for forming, with attenuated physical stress, a silicon nitride oxidation mask which may be employed within a local oxidation of silicon (LOCOS) method for forming a local oxidation of silicon (LOCOS) isolation region within a silicon semiconductor substrate employed within a semiconductor integrated circuit microelectronic fabrication. To realize the foregoing object, the silicon nitride oxidation mask is formed as a multi-layer silicon nitride oxidation mask, where sub-layers within the multi-layer silicon nitride oxidation mask are formed employing different deposition rates.
Desirable in the art of semiconductor integrated circuit microelectronic fabrication are additional local oxidation of silicon (LOCOS) methods through which local oxidation of silicon (LOCOS) isolation regions may be formed with enhanced properties within semiconductor integrated circuit microelectronic fabrication, in particular as directed towards attenuated bird's beak encroachments of local oxidation of silicon (LOCOS) isolation regions beneath silicon nitride oxidation masks employed within the local oxidation of silicon (LOCOS) methods.
It is towards the foregoing object that the present invention is directed.